1. Field of the Invention
The present invention generally relates to techniques for monitoring physical variables associated with the operation of a computer system. More specifically, the present invention relates to a method and an apparatus that accurately infers the outputs of physical sensors that are used to monitor the physical variables using EMI signals.
2. Related Art
Modern server computer systems are typically equipped with a significant number of physical sensors which monitor signals during the operation of the computer systems. For example, most CPUs are currently equipped with on-chip thermal diodes that are used to monitor CPU core temperatures. Other monitored signals can include voltages, currents, fan speeds, and other physical variables associated with the computer system operation. Results from this monitoring process can be used to generate time series data for these signals which can subsequently be analyzed to determine how a computer system is operating. One particularly desirable application of this time series data is for purposes of “proactive fault monitoring” to identify leading indicators of component or system failures before the failures actually occur.
Note that the physical sensors inside computer systems can degrade over time, which can lead to “stuck-at” faults or other failure modes of a physical sensor. In many cases, the mean time between failures (MTBF) of the physical sensors can be shorter than the MTBF for the components or systems that the sensors are designed to protect. However, it is typically not commercially feasible to deploy multiple, redundant physical sensors inside server computer systems to monitor a particular physical variable (unless they are safety critical systems). Consequently, when physical sensors degrade or fail during, service, they have to be replaced to ensure the safety of the computer systems.
Unfortunately, replacing the degraded or failed physical sensors within a computer system may require replacing the complete system boards or field replaceable units (FRU)s which contain these physical sensors. For high-end computer systems, this replacement can be prohibitively costly. For example, the uniboards for high-end server computer systems can cost $100K per board. Note that, it is not practical to replace a $100K system board just because a $2 sensor has failed.
Hence, what is needed is method and an apparatus that facilitates replacing a faulty physical sensor in a computer system without the above-described problems.